Alloy of lead and alkaline earth metal



Patented Aug. 11, 1925.

a if" i WALT HER MATHESI'US, OF CHAR-LOTTENBURG, GERMANY.

ALLOY O'F LEAD AND ALKALINE EARTH METAL.

No Drawing. Application filed May 16,

To all whom it may concern:

Be it known that I, WALTHER MATHESIUS, a citizen of the German Republic,residing at Charlottenburg, Germany, have invented certain new anduseful Improvements in an Alloy of Lead and Alkaline Earth Metal, forwhich I have filed application for-pat-' ent in Germany on January7,192.), of which the following is a specification.

This invention relates to an alloy of lead with metals of the alkalineearths, calcium,

strontium, barium. An alloy of lead with about 3% of calcium, andcontaining also about l3% of cadmium or bismuth or both, has beendescribed in the German Patent No. 297210. A

Metallographic examination of the alloy in question shows thatsubstantially harder crystals are embedded in uniformdistribution in ahomogeneous main mass. On closer examination of the texture, it can beeasily shown that these harder crystals are constituted by an alloy oflead and calcium,

. harden the main lead portion ofthe alloy to a certain extent and. toreduce its melting point, moreover, as owing to the addition even of afew per cent of calcium to lead, the melting point of the latter isconsiderably raised.

A metal of the composition referred to is eminently'suitable, as shownbyexperience, for use-as metal for liningv bearings inthe same manner inwhich the so-called tinwhite metals have been exclusively employed. Asshown by metallographic examination, even *in good tin-white metals, thestructural conditions are exactly the same, only here the hardercrystals are uniformly distributed in the softer main mass, are composedof a copper-tin alloy.

In both cases the harder crystals embedded in the softer main mass,form, during the use of the alloys as bearing metals, those ingredientsof the alloy which, after a' cer- 1921. Serial N0. 469,959.

tain running-in of the shaft has taken place, form the bearing surfaceproper.

Exhaustive experiments have now proved that it is possible to obtainalloys which are eminently suitable for use as bearing metals,exclusively from lead with an addition of calcium, strontium, andbarium, and without cadmium or bismuth. The metals, strontium andbarium, form with lead definite chemical compounds exactly in the sameWay as calcium. Met-allographic examination of the texture of such analloy on a ground surface shows that strontium-lead alloy is exactlysimilar to calcium-lead alloy in a peritectic structure,whilst'barium-lead compound solidifies with the excess of lead at thesame tim to form a eutectic.

The barium-lead compound produces therefore in the alloy chiefly ahardening of the main mass, whilst strontium-lead like calcium-lead,chiefly assists in the formation of harder crystals.

Examination of melting or softening temperatures of such alloys shows,however, that when the alloy solidifies, the three compounds do notcompletely crystallize out of the same, on the contrary some traces ofthe said compounds are still left in the alloy in the state of solidsolution, for a considerable lowering of the melting or softeningtemperature takes place when, in addition to calcium which is mosteasily obtained in large quantities, are also added to the alloy certainquantities of strontium or barium, or preferably, both.

While, the addition of the calcium to the lead increases the meltingtemperature, the addition of two, '(or still better, all three) of thealkalin earth metal ingredients, produces a lowering of the meltintemperature and increases thefluidity" of t e alloy withe in moderatelimits.

On these observations is based the manufacture of a new bearing metalalloy from lead with about 3% calcium or about 1% each of strontium andbarium.

It is possible to produce an alloy of such composition having a degreeof hardness of 3540 Brinell units, the said alloy having a melting pointof 450500 C. and therefore being excellently adapted for use as bearingmetal. 7 g

Metallographic tests have shown that, in an alloy of this kind, anextremely uniform distribution of the harder crystals exists,.

which has heretofore only been true of the ,best tin-white metals. Initself, the propoadded to the lead, or if three such metalshave beenused, it has been considered necessary to further add other metals toaffect the physical roperties of the alloy. It has never before enrealized that, by the addition of calcium to the lead, there can beobtained the formation of the hard lead-calcium crystals and that, bythe addition of barium and strontium, there results a hardening of thebasic mass, and, at the same time, a lowering of the melting point,which is increased considerably by the addition of the calcium. Thiscommercial result which as stated, is reproduced in the metalloaphlcimage, can only be obtained when,

t e proportions stated for the additions of the three alkaline-earthmetals, (viz., about 3% calcium and about 1% each of strontium andbarium), are maintained. The applicant has proven by tests that onlywiththese proportions can an alloy be produced having the desired hardnessof the basic mass and the uniform distribution of the crystals, togetherwith a satisfactory liquidity.

I claim:

1. A lead alloy containing about 3% of calcium and about 1 to 2% ofanother alkaline earth metal, such alloy being substantially free frommetals other than those stated.

2. An alloy of lead containing about 3% of calcium and about 1% each ofstrontium and barium, such alloy being substantially free from metalsother'than those stated.

3. An alloy of lead containing about 3% of calcium, together withsmaller percentages of strontium and barium, such alloybeing-substantially free from metals other than those stated.

In testimony whereofI aflix my signature in presence of two witnesses.

VVALTHER MATHESIUS. Witnesses:

O'r'ro SCHNEIDER, GERTRUD DOMKONSKI.

